Time delay actuator

ABSTRACT

A hydraulic-magnetic time delay actuator for use with circuit breakers, switches or relays, comprising a non-magnetic time delay tube encircled by a solenoid coil. The tube contains a retarding fluid and a magnetic core, the core being movable longitudinally in the tube in response to the magnetic flux generated by the coil. An armature is pivotally located in the magnetic field of the coil and is movable thereby to actuate the relay, circuit breaker or switch. The movable core has formed therethrough an axial bore which houses a valve and forms a seat for the valve adjacent one end of the bore. A helical stop spring, a portion of which has an outer diameter greater than the interior diameter of the bore, is located therein. The stop spring is inserted into the bore by twisting the spring to reduce its diameter while concurrently pushing it into the bore. The spring is held in place in the bore by frictional engagement with the interior surface thereof. The leading edge of the inserted stop spring is located a preselected distance from the valve seat to limit the movement of the valve away from its seat. The stop spring is tapered slightly in the direction of the valve and is formed of a magnetically permeable material in order to increase the efficiency of the actuator.

Unite States Patent [191 Pope [451 Apr. 24, 1973 [54] TIME DELAYACTUATOR [57] ABSTRACT [75 1 llnvemo'r: Ralph Pope, Robbinsvme, NJhydrauhc-magnetic time delay actuator for use with c1rcu1t breakers,swltches or relays, comprlsmg a nonl l g Heineman" Electric p y magnetictime delay tube encircled by a solenoid coil. Trenton, The tube containsa retarding fluid and a magnetic [22] Filed: p' core, the core beingmovable longitudinally in the tube in response to the magnet1c fluxgenerated by the [21] 'Appl. No.: 247,732 coil. An armature is pivotallylocated in the magnetic field of the coil and is movable thereby toactuate the 52 US. (:1. ..335/62, 251/337, 335/239 relay breaker F Themovfible has [51] km Cl Holh 7/03 formed therethrough an ax1al borewhlch houses a valve and forms a Seat for the valve adjacent one end[58] Field of Search ..335/62, 61, 218, of the bore A helical Ste 8 tina onion of which has an outer dlameter greater than the mtenor dlameterof the bore, is located therein. The stop spring is [56] References Cnedinserted into the bore by twisting the spring to reduce vUNITED STATESPATENTS its diameter vvhile concurrently pushing it into the I bore. Thesprmg held in place in the bore by fric- 2,694,789 11/1954 W1lckens..335/2l8 tiona] engagement i the interior surface thereof 3,308,8473/1967 Umam The leading edge of the inserted stop spring is located3,183,931 5/1965 Alford ..l37/612.l

Primary Examiner1-lar0ld Broome Att0rney .loseph G. Denny, III et a1.

a preselected distance from the valve seat to limit the movement of thevalve away from its seat. The stop spring is tapered slightly in thedirection of the valve and is formed of a magnetically permeablematerial in order to increase the efficiency of the actuator.

9 Claims, 3 Drawing Figures O 6 34 23 m 26 I /7 I I I 43 /8 0 l I 42 i3.320 /6 l3 44 Q I 56 I Patented April 24, 1973 2 Sheets-Sheet lBACKGROUND OF THE INVENTION The invention relates generally to circuitbreakers, relays or switches. More specifically the invention relates tocircuit breakers, relays or switches incorporating a hydraulic-magneticactuator comprising a solenoid coil wound around a sealed tubecontaining a movable core and a retarding liquid through which the coreis moved in response to the energization of the coil. The actuator alsoincludes an armature pivotally supported adjacent the tube for movementtoward and away from said tube depending upon the energization ofthesolenoid coil.

The purpose of the retarding liquid is to create a time delay betweenthe energization of the coil at a preselected level and the subsequenttripping of the circuit breaker, or operation of the relay or switchcontacts.

In devices of this type, when the coil is unenergized or energized belowa preselected level, the core is moved by means of a biasing spring toa-position in the tube most remote from the armature. Upon energizationof the coil to a preselected level, however, the movable core is pulledtoward the armature against the bias of the biasing spring by themagnetic flux generated by the coil, but its movement toward thearmature is retarded by means of the retarding liquid which is forced topass through the narrow space between the interior surface of the tubeand the movable core. The rate at which the core moves through the tubeis determined by the viscosity of the retarding liquid. When, after apreselected time, the core reaches the end of the sealed tube nearestthe armature, the circuit breaker, relay or switch, as the case may be,is activated.

When the coil is subsequently de-energized or energized below apreselected level, the core is again moved by the biasing spring towardthe end of the tube most remote from the armature to a reset position.It is, of course, desirableto have the movable core reach its resetposition as rapidly as possible. In order to accomplish this the movablecore is provided with a central bore or passage extending longitudinallythrough the core. A ball-type check valve is located in this passage,the valve being seated or unseated depending upon the direction ofmovement of the COI'Ci- In response to the movement of the core towardthe armature, the valve is moved onto its seat whereby the retardingliquid is blocked from passing through the central passage in the core,while in response to the movement of the core away from the armature,the valve is unseated to permit substantially unobstructed flow of theretarding liquid through the passage.

The invention is directed specifically to a means for limiting themovement of the ball-check valve away valve may move away from its seatso as to permit its rapid return to its seat in response to the motionof the core toward the armature.

A drawback associated with the above noted prior art arrangement is thatit necessitates the accurate drilling of a diametrically disposed holeinto which the stop pin may be inserted, thereby adding to the cost ofthe actuator and the time required to assemble it.

OBJECTS AND SUMMARY OF THEINVENTION A principal object of this inventionis the provision of an improved hydraulic-magnetic time delay actuatorfor use in connection with circuit breakers, switch or relays.

A still further object is to provide an improved means for limiting themovement of a check valve to control the flow of a retarding liquidthrough a movable core in a time delay actuator of the above noted type.

A still further object is to provide a time delay actuator which isinexpensive and easily assembled.

The preferred embodiment of the invention comprises a hydraulic-magneticactuator which includes a hollow non-magnetic tube around which is wounda solenoid coil and in which is contained a movable core and a retardingliquid. The movable core has formed therethrough a central bore in whichis located a check valve. The bore forms a seat near one end thereof onwhich the valve may become seated to obstruct the flow of retardingliquid through said core. A helical stop spring at least a portion ofwhich has an initial exterior diameter greater than the interiordiameter of the bore is twisted against itself to reduce its diameterand is thereby inserted into the bore, the leading edge of the insertedspring being spaced a preselected distance from the seated valve, so asto limit its movement away from the seat when it becomes unseated. Thestop spring is held in place in the bore by frictional engagement withthe interior surfaces thereof. The stop spring may be made of amagnetically permeable material and, in addition, may be tapered in thedirection of the valve seat to further improve the operation of theactuator.

The foregoing and other objects of the invention, the principles of theinvention, and the best mode in which I have contemplated applying suchprinciples will more fully appear from the following description andaccompanying drawings in illustration thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings;

FIG. 1 is a longitudinal sectional view through the casing of thecircuit breaker of the invention, showing the operating mechanism of thecircuit breaker in elevation and including a longitudinal sectional viewof the time delay tube and movable core according to the inventionincorporated therein;

FIG. 2 is an enlarged longitudinal sectional view of the movable coreshowing the details of the check valve and stop spring; and

FIG. 3 is a traverse cross sectional view of the movable core takenalong the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For illustrative purposes, theimproved hydraulicmagnetic actuator according to the invention is shownas being incorporated into a circuit breaker of the type shown in U.S.Pats. Nos. 2,694,789, 2,000,109 and 2,360,922. It should, however, beunderstood that the improved hydraulic-magnetic actuator disclosedherein may be incorporated into various other types of circuit breakers,and in addition, may also be incorporated into various relays andswitches.

Referring to FIG. 1 of the drawings, there is shown a circuit breakercomprising an insulating case 11 and an operating mechanism 12. Theoperating mechanism 12 is described in detail in the prior patents notedabove, among others, and will therefore be described only brieflyimmediately hereinafter.

The circuit breaker operating mechanism 12 comprises a main frame 13which is fixedly supported within the insulating case 11. The frame 13is generally L-shaped, is made of a magnetically permeable material, andis provided with a pair of ears 15 containing holes for carrying a pivotpin 16 on which a switch blade 17 is rockable into and out of engagementwith a stationary contact 18 connected to a line terminal 19. The switchblade 17 is continuously biased in the direction away from engagementwith the contact 18 by a main spring 20.

The switch blade 17 is coupled to an operating handle 21 through anovercenter toggle comprising the links 22 and 23. The handle 21 isintegral with a handle link 24 which is pivotally supported on a pin 25carried in holes in another pair of ears 28 extending from the mainframe 13. The toggle may be latched or locked to form a rigid connectionbetween the handle 21 and the switch arm 17 by means of a latch shaft 26which engages a tooth 27 on the link 22, as explained more fully in U.S.Pat. No. 2,360,922. The latch shaft 26 may be rotated to collapse thetoggle by moving the trip arm 29 thereof, to allow the tooth 27 to movepast the flat face of the shaft 26. If, when the switch blade 17 islocked into contact with the contact 18, the trip arm 29 is so moved,the switch blade -17 will move away from the contact 18 as a result ofthe collapse of the toggle and the biasing action of the main spring 20.

The moving of the trip arm 29 to collapse the rigid toggle and open thecircuit breaker is effected by a hydraulic-magnetic time delay actuator30. The time delay actuator 30 comprises an L-shaped armature 31 havingan attractable arm 32 and an actuating arm 33 and pivotally supportedfrom the main frame 13 on a pin 34. The armature 31 is continuouslybiased for rotation in a counter-clockwise direction by means of aspring (not shown) wound on the pin 34 so that the actuating arm 33 isnormally out of engagement with the trip arm 29 and the attractable arm32 is in abutment with a stop member 36, which limits the rotation ofthe armature 31.

The actuator 30 also includes a time delay tube 41 around which is wounda solenoid coil 40, the time delay tube being supported in an opening inone leg of the L-shaped main frame 13. The armature 31 is, of course,made of a magnetically permeable-material so as to be movable by themagnetic field generated by the solenoid coil 40. As is well known inthe art of circuit breakers, one end of the coil 40 is soldered orotherwise fixedly connected to the switch blade 17 by means of a braidedwire 44, while the other end of the coil 40 is connected to the terminal43.

The time delay tube 41 contains a movable core 42 and a retarding liquid45 and is closed at one end by a magnetic pole piece 46. The core 42 ismade of a magnetically permeable material and is movable longitudinallythrough the retarding liquid 45 in the tube 41 by the magnetic fieldgenerated by the coil 40. The core 42 is biased by a biasing spring 47away from engagement with the pole piece 46, the forepart of the core 42being reduced in diameter to permit passage thereof through the spring47 into contact with the pole piece when the core is in its attractedposition. The core 42 makes a slip fit with the interior surface of thetube, such fit being sufficiently loose to permit slow seepage ofretarding liquid from one side of the core 42 to the other during axialmovement of the core toward the pole piece 46 under the influence of themagnetic field generated by the coil 40. The core 42 has formedtherethrough an axial bore or passage 50 having located therein acheck-type ball valve 51. The bore 50 adjacent one end of the core 42 isnarrowed to form a seat 52 for the valve 51.

Also contained within the bore 50 is a helical stop spring 55whichserves to limit the movement of the ball valve 51 away from itsseat 52. The spring 55 is tapered in diameter in the direction of thevalve 55 and is preferably made of a magnetizable material to furtheradd to the magnetizable mass of the core 42 and thereby improve theoperation of the actuator 30. A least a portion of the spring 55 has anouter diameter, prior to insertion into the bore 50, which is greaterthan the interior diameter of the bore 50.

The stop spring 55 is inserted into the bore by twisting the spring 55on itself to reduce its diameter while concurrently pushing it into thebore 50. In order to facilitate insertion into the bore 50, the stopspring 55 is terminated on its leading or root end 56 with adiametrically disposed tang 57. An inserting tool (not shown) isdesigned to pass through the .stop spring .55 and engage this tang 57during the insertion process. By pushing the spring 55 into the bore 50and concurrently twisting the spring 55 on itself by means of the tang57, the spring 55 is reduced in diameter sufficiently to allow it toenter the bore 50.

The spring 55 is held in place in the bore 50 by frictional engagementwith the interior surface thereof, resulting from the natural tendencyof the spring to return to its original diameter while being restrainedagainst doing so by the smaller diameter of the bore 50. The leadingedge of the inserted stop spring 55 is located a preselected distancefromthe valve seat by means of the inserting tool (not shown) to limitto a preselected distance the movement of the valve away from its seat.

In operation, when the current flow through the solenoid coil 40 reachesa predetermined level the magnetic flux generated thereby causes thecore 42 to move toward the pole piece 46 against the bias of the biasingspring 47. The rate of movement of the core 42 is dependent upon theviscosity of the retarding liquid 45 in the time delay tube 41. Whenrapid movement of the core is desired, a light liquid is employed,whereas when a more retarded movement is desired a more viscous fluidmay be used in the tube. After the lapse of a sufficient amount of timethe core 42 approaches the pole piece 24 sufficiently to decrease thereluctance of the magnetic current to a point where the attractable arm32 of the armature 31 is attracted into contact with the pole piece 46.As the attractable arm 32 moves toward the pole piece 46, the actuatingarm 33 of the armature abuts and moves the trip arm 29, thereby turningthe lock shaft 26 and collapsing the toggle to open the circuit breakercontacts.

When the solenoid coil 40 is de-energized, the core 42 is moved by thebiasing spring 47 away from the pole piece 46 toward its reset positionat the end of the time delay tube 41 most remote from the pole piece 46.During this movement the valve 51 moves away from its seat 52 until itsmovement is limited by the leading end 56 of the stop spring 55, therebypermitting a substantially unimpeded flow of retarding liquid throughthe central bore or passage 50 in the movable core 42. As a result ofthe flow of liquid through the bore 50, the movable core 42 returns toits reset position in an appreciably shorter time than would otherwisebe possible.

Having described this invention, what I claim is:

1. A time delay actuator comprising,

a magnetic frame,

a tube supported from the frame,

a coil encircling said tube,

a pole piece forming a closure for one end of said tube,

an armature pivotally supported from said frame and rotatable toward andaway from said pole piece,

a fluid filling said tube,

a magnetically permeable core in said tube,

said core being movable along the axis of said tube through said fluidunder the influence of the magnetic flux generated by said coil, saidcore including an axial bore therethrough, a ball valve located in saidbore,

said bore forming a seat for said valve, and a helical spring located insaid bore, a portion of said spring having an outer diameter, prior toinsertion into said bore, greater than the inner diameter of said bore,the leading edge of said inserted spring being located a preselecteddistance from said valve seat to limit the movement of said valve awayfrom said seat.

2. The combination recited in claim 1 wherein the outer diameter of saidhelical spring is tapered in the direction of said valve.

3. The combination recited in claim 2 wherein said helical spring ismade of a magnetically permeable material.

4. The combination recited in claim 3 wherein said spring includes adiametrically disposed tang at its leading end, said tang suitable forbeing grasped during insertion of said spring into said bore to reduceits diameter and thereby permit said spring to enter said bore.

5. In a time delay actuator including a time delay tube, a solenoid coilwrapped around said tube, a retarding fluid and a movable magnetic corewithin said tube, a biasing spring for biasing said core to a firstposition in said tube, said core being movable longitudinally throughsaid tube against the bias of said biasing spring to a second positionin response to the magnetic field generated by said coil, said corehaving formed therethrough an axial bore, a valve housed in said bore,said bore forming a seat for said valve, the improvement comprisingresilient means located within said bore on the side of the valveopposite said seat for limiting the movement of said valve away from itsseat when said core moves from said second position to said firstposition, said resilient means being in tensionecl condition while inplace in said bore to exert an outward force against the interiorsurface of said bore to thereby hold said means in place in said bore.

6. The combination recited in claim 5 wherein said resilient meanscomprises a helical stop spring, a portion of said stop spring having anouter diameter, before insertion into said bore, greater than theinterior diameter of said bore.

7. The combination recited in claim 6 wherein said stop spring istapered in diameter with the leading end of said inserted spring havinga smaller diameter than the trailing end of said inserted spring.

8. The combination recited in claim 7 wherein said spring is made of amagnetically permeable material.

9. The combination recited in claim 8 wherein the leading end of saidinserted spring includes a diametrically disposed tang.

1. A time delay actuator comprising, a magnetic frame, a tube supportedfrom the frame, a coil encircling said tube, a pole piece forming aclosure for one end of said tube, an armature pivotally supported fromsaid frame and rotatable toward and away from said pole piece, a fluidfilling said tube, a magnetically permeable core in said tube, said corebeing movable along the axis of said tube through said fluid under theinfluence of the magnetic flux generated by said coil, said coreincluding an axial bore therethrough, a ball valve located in said bore,said bore forming a seat for said valve, and a helical spring located insaid bore, a portion of said spring having an outer diameter, prior toinsertion into said bore, greater than the inner diameter of said bore,the leading edge of said inserted spring being located a preselecteddistance from said valve seat to limit the movement of said valve awayfrom said seat.
 2. The combination recited in claim 1 wherein the outerdiameter of said helical spring is tapered in the direction of saidvalve.
 3. The combination recited in claim 2 wherein said helical springis made of a magnetically permeable material.
 4. The combination recitedin claim 3 wherein said spring includes a diametrically disposed tang atits leading end, said tang suitable for being grasped during insertionof said spring into said bore to reduce its diameter and thereby permitsaid spring to enter said bore.
 5. In a time delay actuator including atime delay tube, a solenoid coil wrapped around said tube, a retardingfluid and a movable magnetic core within said tube, a biasing spring forbiasing said core to a first position in said tube, said core beingmovable longitudinally through said tube against the bias of saidbiasing spring to a second position in response to the magnetic fieldgenerated by said coil, said core having formed therethrough an axialbore, a valve housed in said bore, said bore forming a seat for saidvalve, the improvement comprising resilient means located within saidbore on the side of the valve opposite said seat for limiting themovement of said valve away from its seat when said core moves from saidsecond position to said first position, said resilient means being intensioned condition while in place in said bore to exert an outwardforce against the interior surface of said bore to thereby hold saidmeans in place in said bore.
 6. The combination recited in claim 5wherein said resilient means comprises a helical stop spring, a portionof said stop spring having an outer diameter, before insertion into saidbore, greater than the interior diameter of said bore.
 7. Thecombination recited in claim 6 wherein said stop spring is tapered indiameter with the leading end of said inserted spring having a smallerdiameter than the trailing end of said inserted spring.
 8. Thecombination recited in claim 7 wherein said spring is made of amagnetically permeable material.
 9. The combination recited in claim 8wherein the leading end of said inserted spring includes a diametricallydisposed tang.